Method for incinerating industrial wastage

ABSTRACT

There is disclosed a method for incinerating combustible industrial wastage containing organic nitrogen compounds of a peptide bond, cyan radical, etc. by using a so called fluidized bed incineration furnace. This method uses steps of supplying, the aforesaid wastage together with combustible materials abundant in carbon content, such as pulverized coal, heavy oil, etc., in the fluidized bed to thereby maintain the interior of the fluidized bed in a reductive atmosphere, while reducing nitrogen oxide produced from the combustion of the wastage, whereby nitrogen oxide may be removed as innocuous nitrogen from waste-gas or stack gas.

United States Patent 1191 Kishigami et al.

1111 3,888,194 1 1 June 10, 1975 1 1 METHOD FOR INCINERATING 3.3062362/1967 Campbell t. 110/8 3,515,381 6/1970 Foch 1 1 .v 110/8 X INDUSTRIALWASTAGE 3,589,313 6/1971 Smith et a1 v 1 110/8 [75] Inventors: KunioKishigami; Hiroshi 3,772,998 11/1973 Menigat 110/8 Kobayashi; ToruSente; Koichi 3,776,150 12/1973 Evans et a1. 1 10/28 X Sugiyama, all ofYokohama, Japan [73] Assignee: Babcock-Hitachi K.K., Tokyo, PrimaryExaminer kfenneth Sprague Japan Attorney, Agent, or Firm-Thomas E.Beall, Jr. 2 Fl d: F 2] 1e eb 28,1974 ABSTRACT [21 1 Appl' 446'895 Thereis disclosed a method for incinerating combustible industrial wastagecontaining organic nitrogen [30] Foreign Application P i it D tcompounds of a peptide bond, cyan radical. etc. by Nov 2L I973 Japan48430187 using a so called fluidized bed incineration furnace. Thismethod uses steps of supplying. the aforesaid [52] CL n "0/8 F; I [0/281 10/49 wastage together with combustible materials abundant l 10/8 6 incarbon content, such as pulverized coal, heavy oil, [5 H CL H F23g etc.,in the fluidized bed to thereby maintain the inte- [58] n w of Search n0/7 R 8 R 18 R 28 J rior of the fluidized bed in a reductive atmosphere,1 0/119 while reducing nitrogen oxide produced from the combustion ofthe wastage, whereby nitrogen oxide [56] References Chad may be removedas innocuous nitrogen from waste-gas UNITED STATES PATENTS Stack 2729,428 1/1956 Milmorc 2. 122/4 x 7 Claims, 3 Drawing Figures 10 I./' I1 1 1 1 l 1 4 1 1 i 8 1 I 130 19 M 5 0 "2Q 60 i 7 l 1 1 14 5 1 2131 ,5 11' 1 i I i 2 1 I 12O /1 1 1 1 l 1 1 19b 6b 17 1 1s 2 1 :15 r 1 p 1 v /11 1 9 we 2 PATENTEDJUN 10 I975 FIG.

FIG. 3

METHOD FOR INCINERATING INDUSTRIAL WASTAGE BACKGROUND OF THE INVENTIONI. Field of the invention This invention relates to a method forincinerating in a fluidized bed furnace the industrial wastagecontaining organic nitrogen compounds which produce, upon incineration,a great quantity of nitrogen oxide detri mental to the human body, andmore particularly to a method for reducing and removing nitrogen oxidethus produced, by maintaining the interior of a fluidized bed in areductive atmosphere. thereby minimizing the quantity of nitrogen oxidecontained in the combustion waste-gas.

2. Description of the prior art Hithereto, it has been a generalpractice to use an incineration method for treating muddy industrialwastage, and such incineration has been admitted as the most reasonablemethod which finds a wide use of this kind. The most common incinerationfurnace for use to this end is of a fluidized bed type. In the fluidizedincineration furnace, air is blown from below through the incombustiblefluidizing medium particles placed on a perforated plate provided in thefurnace, to fluidize same, while the interior of the fluidized bed ispreheated by means such as a burner to a temperature higher thancombustion temperatures of the materials to be burnt, and the materialsto be burnt are fed into the furnace from its top, whereby the materialsto be burnt may be incinerated due to a combustion heat produced fromthe burning materials themselves. In other words, the fluidized bedfurnace as used herein is an incineration furnace using a fluidized bed.

Contained in the recent industrial wastage, particularly in the muddyeffluent from various kinds of effluent treating apparatuses are a smallamount of sulfur, chlorine and nitrogen in addition to carbon andhydrogen which are combustible matters.

Those elements are not present in the form ofa single substance but ascomplicated compounds. Those may be generally classified into biologicalcompound such as protein and artificial compounds such as polyamideresin.

The organic nitrogen compounds contained in the industrial wastage suchas for instance protein, polyamide resin, sewage sludge, acrylic resin,etc., are present in the form ofa peptide bond (CO. NH), cyan radical(-CN), ammoniacal nitrogen (NH, nitric and nitrous nitrogens (NO;;, NOand the like, and the incineration of such organic nitrogen compoundswould leads to the production of nitrogen oxides (NO which aredetrimental to a human body and of a quantity which is commensurate tothat of nitrogen contained in the materials to be burnt.

Experiments reveal that the aforesaid wastage produces NO,, even whenburnt at a temperature as low as 750 to 850C, because of the bondingcondition of the nitrogen contained therein. The production of NO is dueto the reaction of organic nitrogen compounds contained in the wastagewith oxygen, during combustion. Thus, it should be noted that themechanism of the production of NO, is fundamentally different in itsmechanism from a phenomenon. wherein inorganic nitrogen contained in airis oxidized at an elevated ternpcrature to produce NO,.

The nitrogen oxides (NO which are produced due to the oxidation ofinorganic nitrogen contained in air during the combustion process in ageneral type industrial furnace such as a boiler are negligible inquantity in the case of a temperature being below l,()00C, whereas inthe case of the temperature being over l,000C, the quantity of nitrogenoxides (NO,] produced is notably increased. This is because nitrogen (Nand oxygen (0 in air react with each other at an elevated temperaturesuch as above l,(l()()C according to the following formula, therebyproducing NO:

On the contrary, nitrogen oxides (NO produced from the combustion oforganic nitrogen compounds contained in muddy wastage exhausted fromvarious kinds of effluent treating apparatuses are not like those whichare produced from the oxidation of nitrogen in air at an elevatedtemperature but those which are produced from the decomposition oforganic nitrogen compounds contained in the muddy wastage. Accordingly,nitrogen oxide may be produced at any level of a lower temperature, asfar as the muddy wastage is in the range of temperatures, at which it iscombustible.

As a result, nitrogen oxides which are produced from the oxidation ofnitrogen with oxygen in air during the combustion in the industrialfurnaces of a general type may be prevented to some extent from beingproduced by lowering the combustion temperature to not more than l,000C.In contrast thereto, nitrogen oxides which are produced from thecombustion of organic nitrogen compounds may not be prevented fromproduction simply by resorting to a measure to lower the temperature.

Accordingly, it is an object of the present invention to provide amethod for incinerating industrial wastage containing organic nitrogencompounds therein, said method being adapted to prevent the productionof the nitrogen oxides to a possibly minimized extent.

For a consideration of what is believed to be novel in the presentinvention, attention is directed to the following description and theclaims appended thereto in connection with the accompanying drawings.

SUMMARY OF THE INVENTION According to the present invention, there isprovided a method for incinerating industrial wastage, in which air isblown into a furnace from below to fluidize incombustible fluidizingmedium particles placed in the furnace, thereby forming a fluidized bed,while said industrial wastage is introduced in the fluidized bed fromthe top of the fluidized bed incineration furnace which has beenpreheated to a temperature above a combustion temperature of combustibleindustrial wastage to be burnt, and then the aforesaid wastage is burntdue to the combustion heat produced from the wastage itself, said methodbeing characterized in that combustible materials abundant in carboncontent is supplied together with the aforesaid wastage into thefurnace, thereby maintaining the interior of the fluidized bed in areductive atmosphere whereby the nitrogen oxides produced from thecombustion of organic nitrogen contained in the aforesaid wastage may bereduced to an innocuous nitrogen and thus nitrogen oxide may be removedfrom the combustion waste gas.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a magnified view ofa muddyparticle within a fluidized bed incineration furnace, embodying thepresent invention;

FIGv 2 is a view illustrating the conditions within a fluidized bedincineration furnace embodying the present invention; and

FIG. 3 is a schematic view illustrating an operational system and thecross section of a fluidized bed incineration furnace embodying theinvention.

DETAILED DESCRIPTION OF THE INVENTION The present invention is directedto providing a method for incinerating industrial wastage containingorganic nitrogen compounds, by using a fluidized bed furnace, in whichindustrial wastage together with ma terials containing a great amount ofcarbon, such as pulverized coal, heavy oil or the like is charged in afurnace to thereby fluidized the wastage and the carbon abundantmaterial together with fluidizing medium with air, and then theindustrial wastage is burnt, while the interior of the fluidized bed (orfluidized layer) is maintained in a reductive atmosphere, whereby thenitrogen oxides (NO,,.) produced from the organic nitrogen compoundscontained in the wastage are reduced during the combustion of thewastage, to thereby obtain nitrogen gas (N thus preventing theproduction of nitrogen oxides.

As is well know, the fluidized bed is provided by blowing air or gasinto a furnace from its bottom and fluidizing the fluidizing medium inthe form of solid particle layer which is supported on a perforatedplate within a furnace. In general, silica base particles (primaryconstituent SiO such as river sand, which is chemically inactive, areused as a fluidizing medium of a solid particle layer, the particle sizethereof being in the range from 0.1 to 2.0 mm. In case sulfur and chlorine are contained in the wastage and desired to be directly fixed andabsorbed within the fluidized bed, it is preferable that chemicallyactive cement clinker parti' cles be used as a fluidizing medium. Thecomposition of cement clinker particles is, for instance, 60 to 70% CaO,6 to 8% Fe O and 3 to 6 SiO The fluidized bed incineration furnaceutilizes a fluidized bed for incineration. The temperature of thefluidized bed is normally in the range from 750 to 850C. In the respect,such a temperature is extremely lower than the temperature (over1,000C), at which nitrogen oxides are formed by the reaction of nitrogenwith oxygen contained in air, as is the cases with industrial furnacesof a general type, such as a boiler. Furthermore, at such a lowtemperature, the quantity of nitro gen oxides produced according to thereaction of nitrogen with oxygen in air is neglisible.

What is of consequence in this respect is the production of nitrogenoxides due to the combustion of organic nitrogen compounds contained inthe wastage, because as has been described earlier, nitrogen oxides maybe produced in a great quantity even at a temperature as low as 750 to850C.

Vigorous reaction may be achieved in the fluidized bed furnace, becausethe fluidizing solid particle layer consists of particles of a size from0.l to 2.0 mm and thus presents extremely large contact surface area atthe time when the particle layer stands still (e.g., the height of thelayer is 500 to 1,000 mm). Accordingly,

even the wastage such as those having poor combustibility, like adehydrated mudcake (water content: to may be burnt at a very lowexcessive air ratio l l to 1.3). In case a dehydrated mud'cake having ahigh water content and containing materials having a high carbon contentis burnt in the fluidized bed, the follow ing reaction formulae areconsidered to take place, because the combustible solid matter in themud consists essentially of carbon, hydrogen, sulfur and nitrogen;

However, in practice. the wastage particles are maldistributedmicroscopically to some extent, despite that muddy wastage has beendried. crushed and placed within the fluidized bed. Furthermore, thewastage particles are subjected to combustion at a very small ex cessiveair ratio, such that a reductive atmosphere short of oxygen encirclesaround the small particles of crushed wastage.

Such a condition will be described in more detail with reference todrawings, FIG. 1 is a magnified view of a mud piece b, showing thecondition within a fluidized a, microscopically. Mud pieces b float inthe fluidizing medium particle group d forming a fluidized bed a, whilea mud piece b containing a considerable amount of carbon componentsforms a reductive atmosphere in its surrounded zone c.

On the other hand, there are present in the fluidized bed gas componentssuch as CH CO, H etc., produced due to decomposition of wastage, and theafore said gas components asist in enhancing the effectiveness of thereductive atmosphere.

The fluidized bed itself has a strong catalytic action. There arecontained Fe O and AI O in the aforesaid active fluidizing mediumparticles or vanadium oxide (V 0 formed by vanadium (V) in the heavy oilin said medium particles, if heavy oil is used for auxiliary burning,and those compounds act as catalysts to accelerate the formation ofcarbon monoxide according to the following formulae:

C H O C0 H (water gas reaction) In other words, for incineration of mudcake having a high water content, materials abundant in carbon content,such as pulverized carbon, or waste activated carbon, if required, heavyoil are supplied together with muddy wastage in the fluidized bed, orotherwise the mixture of muddy wastage and materials abundant in carboncontent may be supplied into the fluidized bed for combustion at a smallexcessive air ratio, whereby a great quantity of CO is produced in thefluidized bed for selective reduction of nitrogen oxides according tothe following formulae:

2N0 CO NO CO In addition, hydrogen produced according to the aforesaidwater gas reaction and methane which are produced from hydrocarbon(C,,h,,,) contained in combustible materials in the reductiveatmosphere. reduce nitrogen oxides as follows:

Fe O (W MnO, A1 0 V 0 C11 0 and the like are considered to be catalystsadapted to accelerate the above reactions.

Description will now be given by referring to FIG. 2 showing thecondition of the interior of a fluidized bed incineration furnace foruse in muddy wastage incineration.

In the fluidized bed incineration furnace e, the primary air g of thecombustion air is fed into the incineration furnace e from below forfluidizing the fluidizing medium within the furnace 0, thereby forming afluidized bed k. The fluidized bed It is preheated by means of a burnersor the like. Materials abundant in carbon content such as pulverizedcoal or the like is supplied together with muddy wastage from the top ofthe furnace e into the fluidized bed It to be fluidized together withthe fluidizing medium and incomplete combustion results, whereby theinterior of the fluidized bed It is maintained in a reductiveatmosphere. Thus, the incineration is carried out in this manner. Inthis case, there are present in the form of mixture CO, H CH 0 N and COwithin the fluidized bed k, such that the formation of the reductiveatmosphere within the fluidized bed k may be accelerated.

Furthermore, when the secondary airfis supplied to the upper space overthe fluidizing bed in the fornace e, if 1 ()t is Excess Air Factor) inzone] defined by the upper surface of the fluidized bed It and the inletof the secondary air f, CH and the like which have entered this zonewill be decomposed and burnt. The combustion will further proceed in thezone 1' above the zonej, and waste gas it containing CO H O, N and O isexhausted from the furnace.

One of example of the fluidized bed muddy wastage incineration apparatuswill be described in detail with reference to FIG. 3, hereinafter.

An incineration furnace 1 includes a perforated plate 2 and an airchamber 3 in the lower portion thereof, while the dehydrated mud, whichcontains pulverized coal or fine granular coal. is supplied from the topportion of the incineration furnace 1 therein from a mud supply device4. The air which is required for fluidizing and combustion is suppliedthrough a blower 8, damper l5 and duct 9 to the air chamber 3, therebyfluidizing by passing through the perforated plate 2 the fluidizingmedium particles such as cement clinker and the like as well as the mudwhich contains pulverized coal and fine granular coal, said particlesand mud being positioned on the perforated plate 2, and thus thefluidized bed is provided. The operation of the incineration furnacebegins with heating the fluidized bed by using a burner 6a. after whichthe incineration of the wastage proceeds due to the combustion of thepulverized coal (or fine granular coal) mixed with the muddy wastage. Ifthe heat accruing from the combustion of the pulverized coal isinsufficient. a burner 6a is used as an auxili ary means. The waste gasis discharged through a duct 7 out of the furnace.

When the increase in the quantity of fluidizing gas is required forforming a fluidized bed 5. the waste gas is introduced from duct 7. tothereby supply the waste gas through a damper l4 and blower 16 into theduct 9.

For operation of the incineration furnace 1, it is required to controlthe quantity of air and waste gas to be mixed therewith. To this end, asignal 11 which represents the supplied amount of muddy wastage and isobtained in connection to R.P.M. of a rotary feeder of the muddy wastagesupply device 4, and a temperature. signal 18 from a thermometer 1adapted to measure temperatures at the fluidized bed 5, are fed into acontrol box 10, whereby inlet dampers l5 and 14 of the blowers 8 and 16are each controlled by means of signals 12a and 12b, while the controlvalves l9a and 19b for controlling the amount of oil for burners 6a and6b are controlled by means of signals 13a and BI). The burner 6a isprimarily used for starting a furnace or for an auxiliary purpose, whilethe burner 6b is used for supplying combustible materials abundant incarbon content, such as heavy oil, to the fluidized bed 5 and isnormally used in case the muddy wastage to be charged in the furnace 1contains no pulverized coal or the like. On the other hand, a damper 22provided in the secondary air supply duct 21 is controlled by means of asignal 20.

As is apparent from the foregoing description, the features of thepresent invention reside in that, for in cineration of combustibleindustrial wastage containing organic nitrogen, particularly muddyindustrial wastage of a high water content; there is used a fluidizingbed which permits the incineration at an extremely low excessive airratio (1.1 to L3); carbon components of no less than 20% by weight,based on the weight of the wastage, are mixed with the solid matter suchas muddy wastage to thereby form a reductive atmosphere within thefluidized bed 5, while the temperature at the fluidized bed 5 ismaintained to be not less than 500C to incinerate the wastage; nitrogenoxides produced are reduced by CO, H CH and the like which are thusproduced; whereby nitrogen oxides may be removed from the wastecombustion gas from the wastage in the form of nitrogen gas. Accordingto another aspect of the invention, there are used, asfluidizing-medium, cement clinker particles containing a great amount ofFe O C50 MnO, A1 0 chrominum ore particles and manganese ore particlesfor the purpose of accelerating the aforesaid reductive reaction,thereby effectively reducing and removing nitrogen oxides.

The reactions which take place within the fluidized bed incinerationfurnace according to the present invention are summerized as follows:The following reactions take place for the combustible matter and theadded carbon components, within the reductive fluidized bed which ismaintained at a temperature of not less than 500C:

wherein C H represents hydrocarbon groups contained in the combustiblematters, part of which is subjected to dry destillation anddecomposition within the fluidized bed under a reductive atmosphere tothereby produce methane (CH and the like.

CO. H CH, which are produced from the aforesaid reactions maintain thefluidized bed in a reductive atmosphere, whereby nitrogen oxidesproduced simultaneously with the production of the aforesaid gases arereduced according to the following reactions:

2N0 +CO N CO:

N 0 CO N CO 2N0 2H N 2H O CH 4N0; 4N0 CO ZH- O CH 4N0 2N CO ZH O Thequantity of CO produced within the fluidizing bed according to the abovereactions in much great as compared with that of nitrogen oxide, suchthat excessive CO, H C H CH and the like are oxidized by means of thesecondary air in a space over the upper surface of the fluidized bed tobe converted into CO and H 0 to present harmless gases.

When incinerating sewage mud having a water content of 78%, solid matterof 22% and nitrogen content in solid matter, of 5.5%. by using the abovefluidized bed incineration furnace, the concentrations of nitrogenoxides (NO,) in the waste gas are as follows:

when pulverized coal is added 65 ppm when pulverized coal is not added1,230 ppm It will be understood that the above description is merelyillustrative of preferred embodiments of the invention. Additionalmodifications and improvements utilizing the discoveries of the presentinvention can be readily anticipated by those skilled in the art fromthe present disclosure, and such modifications and improvements mayfairly be presumed to be within the scope and purview of the inventionas defined by the claims that follow.

What is claimed is:

1. In a method for incinerating combustible industrial wastagecontaining organic nitrogen compounds in a fluidized bed, wherein airfor use in combustion is blown into a furnace from below to fluidizednoncombustible fluidizing medium placed within said furnace. for forminga fluidized bed, and at the same time said combustible industrialwastage is supplied into said furnace from the upper portions thereof,which furnace has been preheated to a temperature above the combustiontemperature of said combustible industrial wastage which is to beincinerated in said fluidizing bed, the improvements comprising thesteps of: supplying combustible fuel material abundant in carbon contentwith said combustible industrial wastage into said fluidized bed;simultaneously maintaining the interior of said fluidized bed in areductive atmosphere and at a temperature higher than the combustiontemperature of said fuel material and the combustion temperature of saidcombustible industrial wastage; incinerating said combustible industrialwastage in the reductive atmosphere in said fluidized bed and producingnitrogen oxides from the combustion of the organic nitrogen compoundscontained in said combustible industrial wastage and reducing thenitrogen oxides thus obtained from the organic nitrogen compounds withinthe reductive atmosphere of the fluidized bed and thereby removing thenitrogen oxides from the combustion gas produced by the combustion ofsaid combustible industrial wastage and said fuel materials abundant incarbon content.

2. A method for incinerating industrial wastage as defined in claim 1,including the step of providing said flu idized medium particles ascement clinker particles. which contain Fe O Al O Cr O and MnO ascataylsts.

3. A method for incinerating industrial wastage as defined in claim 1,including the further step of providing said fluidized medium particlesas chromium ore particles.

4. A method for incinerating industrial wastage as defined in claim 1,further including the step of providing said fluidized medium particlesas manganese ore particles.

5. A method for incinerating industrial wastage as de fined in claim I,wherein the resultant combustion gases obtained from the prior steps aremixed with air and maintained at a temperature above the combustiontemperature of the combustible gases and below l,000 C for completingthe combustion of the combustible gases without producing nitrogenoxides from the nitrogen gas.

6. A method for incinerating industrial wastage as defined in claim 5,wherein the resultant gases from the previous steps are at least in partsupplied with the air blown into the furnace to fluidize thenon-combustible fluidizing medium placed within said furnace and furtherto control the oxygen content of the fluidizing gas.

7. A method for incinerating industrial wastage as defined in claim 1,including the further step of automatically controlling the quantity ofcombustible fuel material abundant in carbon content that is supplied tothe fluidized bed and simultaneously automatically controlling theoxygen content of the fluidizing air blown into the furnace from below,in response to the flow of industrial wastage into the furnace and thetemperature of the fluidized bed.

1. IN A METHOD FOR INCINERATING COMBUSTIBLE INDUSTRIAL WASTAGECONTAINING ORGANIC NITROGEN COMPOUNDS IN A FLUIDIZED BED, WHEREIN AIRFOR USE IN COMBUSTION IS BLOWN INTO A FURNACE FROM BELOW TO FLUIDIZEDNON-CONBUSTIBLE FLUIDIZED MEDIUM PLACED WITHIN SAID FURNACE, FOR FORMINGA FLUIDIZED BED, AND AT THE SAME TIME SAID COMBUSTIBLE INDUCTRIALWASTAGE IS SUPPLIED INTO SAID FURNACE FROM THE UPPER PROTIONS THEREOF,WHICH FURNACE HAS BEEN PREHEATED TO A TEMPERATURE ABOVE THE COMBUSTIONTEMPERATURE OF SAID COMBUSTIBLE INDUSTIAL WASTAGE WHICH IS TO BEINCINERATED IN SAID FLUIDIZING BED, THE IMPROVEMENTS COMPRISING THESTEPS OF SUPPLYING COMBUSTIBLE FUEL MATERIAL ABUNDANT IN CARBON CONTENTWITH SAID COMBUSTIBLE INDUSTRIAL WASTAGE INTO SAID FLUIDIZED BED;SIMULTANEOUSLY MAINTAINING THE INTERIOR OF SAID FLUIDIZED BED IN AREDUCTIVE ATMOSPHERE AND AT A TEMPERATUE HIGHER THAN THE COMBUSTIONTEMPERATURE OF SAID FUEL MATERIAL AND THE COMBUSTION TEMPERATUE OF SAIDCOMBUSTIBLE INDUSTRIAL WASTAGE; INCINERATING SAID COMBUSTIBLE INDUSTRIALWASTAGE IN THE REDUCTIVE ATMOSPHERE IN SAID FLUIDIZED BED AND PRODUCINGNITROGEN OXIDES FROM THE COMBUSTION OF THE
 2. A method for incineratingindustrial wastage as defined in claim 1, including the step ofproviding said fluidized medium particles as cement clinker particles,which contain Fe2O3, Al2O3, Cr2O3 and MnO as cataylsts.
 3. A method forincinerating industrial wastage as defined in claim 1, including thefurther step of providing said fluidized medium particles as chromiumore particles.
 4. A method for incinerating industrial wastage asdefined in claim 1, further including the step of providing saidfluidized medium particles as manganese ore particles.
 5. A method forincinerating industrial wastage as defined in claim 1, wherein theresultant combustion gases obtained from the prior steps are mixed withair and maintained at a temperature above the combustion temperature ofthe combustible gases and below 1,000* C for completing the combustionof the combustible gases without producing nitrogen oxides from thenitrogen gas.
 6. A method for incinerating industrial wastage as definedin claim 5, wherein the resultant gases from the previous steps are atleast in part supplied with the air blown into the furnace to fluidizethe non-combustible fluidizing medium placed within said furnace andfurther to control the oxygen content of the fluidizing gas.
 7. A methodfor incinerating industrial wastage as defined in claim 1, including thefurther step of automatically controlling the quantity of combustiblefuel material abundant in carbon content that is supplied to thefluidized bed and simultaneously automatically controlling the oxygencontent of the fluidizing air blown into the furnace from below, inresponse to the flow of industrial wastage into the furnace and thetemperature of the fluidized bed.